The Who, What, Where, When and Sometimes, Why.

Birthweight

Studies show women with a higher birthweight (a woman’s weight when she was born) have an increased risk of breast cancer (especially before menopause) [47-51].

A higher birthweight does not appear to be linked to higher estrogen levels in adulthood [52-54]. However, birthweight may be a marker of factors related to growth (such as adult height) that affect breast cancer risk [53,55-56].

Other reasons behind a link between birthweight and breast cancer risk are under study.

Learn about other early life exposures and breast cancer risk

For a summary of research studies on birthweight and breast cancer risk, visit the Breast Cancer Research Studies section.